1. Field of the Invention
The present invention relates to an address detection circuit and an address detection method.
2. Description of Related Art
In order to execute reading and writing of data on an optical disk with high accuracy, it is required to detect a position on the optical disk with high accuracy. To detect the position on the optical disk, address information that indicates the position on the optical disk needs to be read out from the optical disk itself.
A method of storing the address information in the optical disk includes (1) a method of modulating wobbles meandering along with a data track, and (2) a method of writing address information on a data track. The position on the optical disk can be detected by reading out the address information stored in the optical disk.
In the optical disk, a spiral data track is formed beforehand. The data track is formed by the extension of convex and concave parts formed in the optical disk. More specifically, the data track is formed on a bottom surface of the concave part and/or an upper surface of the convex part. The wobbles are formed by modulating edges of the convex part along with an extending direction of the convex part.
Japanese Unexamined Patent Application Publication No. 2005-50469 (hereinafter referred to as patent document 1), Japanese Unexamined Patent Application Publication No. 2003-85749 (hereinafter referred to as patent document 2), and Japanese Unexamined Patent Application Publication No. 2002-329329 (hereinafter referred to as patent document 3) each discloses a technique of obtaining an address from an optical disk.
The patent document 1 discloses an address detection method which prevents an interruption of a processing caused by an error such as offtrack when a synchronized state of an address becomes unstable due to a state of recording data. The patent document 2 discloses a technique of providing a reproducing apparatus with high reliability of address information of an ADIP. The patent document 3 discloses a technique for reliably detecting a synchronization mark even when user data is recorded in a recording region through a random shift and for reliably reproducing the user data in accordance with the detected synchronization mark.
By the way, in order to detect the address information that indicates the position on the optical disk in a short time, the address may be detected from a signal that is read out from the data written in the data track (hereinafter referred to as data signal). However, data stored in the data track may be stored in a position that is widely apart from a basis position that indicates recording start/end positions or the like of the data that is set in advance in the optical disk. When the address is detected based on such a data, the recording data may be rewritten in a position that is widely apart from the basis position unless any correction processing is carried out. If the data is repeatedly rewritten under such condition, there may be occurred a phenomenon such as gap or overwriting of the recorded data, which may deteriorate the recording quality in the optical disk.
This problem may be addressed by correcting a timing of acquiring the address. However, as the deviation amount of the data with respect to the basis position is uncertain, it may not be possible to deal with the deviation of the data even when the address is detected with an offset by a certain period.
Note that, it may be achieved to suppress degradation of the recording quality of the optical disk by detecting the address from the ADIP (Address In Pre-groove) signal which is readout from a wobble formed in the optical disk, because the timing can be obtained in accordance with the aforementioned basis position. However, in this case, relatively long time is required to detect the address information. As a result, detection of the position on the optical disk in a short time may be inhibited.